Reinforced TN-502RDM-H mobile MOSFETs (Best Medical Canada Ltd., Ontario, Canada) and Gafchromic MD-55-2 film (International Specialty Products, NJ, USA) were used as a redundant in vivo treatment verification system. The absorbed doses used in the calibration procedure were accurately measured by a medical physicist using routine dosimetric equipment following the International Atomic Energy Agency’s TRS-398 protocol [
16] immediately before irradiating the dosimeters. MOSFETs were read by selecting the standard sensitivity bias setting [
17]. A third-order polynomial relationship between pixel value, read in the red channel, and absorbed dose was used to calibrate the film. Films, cut into 1.5 cm × 1.5 cm pieces, were read by an Epson perfection V700 Photo flatbed digitizer (Seiko Epson Corporation, Nagano, Japan). An Elekta Precise fixed linear accelerator (linac; Elekta AB, Stockholm, Sweden) was used both for calibrations and treatments. The linac is equipped with dedicated trays, capable of allocating cylindrical applicators of 3, 4, 5, 6, 7, 8, 9, 10, 12, and 15 cm in diameter and 5 mm in thickness, made of polycarbonate (MCP Iberia S.A., Madrid, Spain). All of them have interchangeable distal ends with no bevel, a 30°-bevel, and a 45°-bevel which result in a nominal source-to-applicator-end distance of 135 cm. The table used for treatments was a SU-14 movable operating table equipped with 150 mm diameter wheels with one directional wheel (Famed Żywiec Sp. z o. o., Żywiec, Poland).